--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Thu Sep 22 10:57:37 2011 -0700
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp	Fri Sep 23 16:07:49 2011 -0400
@@ -597,7 +597,10 @@
 
 public:
 
-  G1MonitoringSupport* g1mm() { return _g1mm; }
+  G1MonitoringSupport* g1mm() {
+    assert(_g1mm != NULL, "should have been initialized");
+    return _g1mm;
+  }
 
   // Expand the garbage-first heap by at least the given size (in bytes!).
   // Returns true if the heap was expanded by the requested amount;